Browse Prior Art Database

Thermosensing Element

IP.com Disclosure Number: IPCOM000093139D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Blum, SE: AUTHOR

Abstract

In those instances where the temperature of a furnace is sensed and controlled by a thermocouple, the latter is made of an expensive metal such as platinum. However, when sensing temperatures of the order of 1700 degrees C, such platinum thermocouples, when operated for many consecutive hours, tend to recrystallize and fracture.

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Thermosensing Element

In those instances where the temperature of a furnace is sensed and controlled by a thermocouple, the latter is made of an expensive metal such as platinum. However, when sensing temperatures of the order of 1700 degrees C, such platinum thermocouples, when operated for many consecutive hours, tend to recrystallize and fracture.

An alternate thermosensing device is a light pipe 2 consisting of a sapphire rod, Al(2)O(3), encased in a highly refractive ceramic material 4. Pipe 2 and casing 4 are lowered in furnace 6 in a well that is in contact with or very close to the substance in furnace 6 whose temperature is to be monitored. Pipe 2 conducts the radiant energy of the heated substance upward and focuses such radiant energy onto bead 8 located in thermopile 10. Bead 8 is blackened to better absorb the radiant energy transmitted by pipe 2. Electrical leads 12 and 14 are attached to bead 8 and a DC voltage is produced across them due to changes in temperature in bead 8. Battery 16 provides a bucking voltage to this heat-generated DC voltage. Thermopile 10 is initially set to a reference temperature as are controls 18.

Voltage outputs are produced by controls 18 when the radiant energy sensed by bead 8 is above or below a predetermined value. Such voltages are applied to feedback circuits for altering currents sent to heating coils, not shown, for the furnace. This type of light pipe sensing device is particularly desirable in the growing of Ga...